For centuries, whales have been hunted for meat and as a source of raw materials. By the middle of the 20th century, however, industrial whaling had left many species seriously endangered, and whaling was ended in all but a few countries. Several organizations have been founded to try to eliminate hunting of whales and other threats to whales’ survival.

The Blue Whale is the largest known mammal that has ever lived, and the largest living animal, at up to 35 m (105 ft) long and 150 tons.

Whales generally live for 40–90 years, depending on the species, and on rare occasions live over a century. Recently a fragment of a lance which had been used by commercial whalers in the 19th century was found in a bowhead whale off Alaska, showing the whale to be between 115 and 130 years old. Furthermore, a technique for dating age from aspartic acid racemization in the whale eye, combined with a harpoon fragment, indicated an age of 211 years for one male, making bowhead whales the longest lived extant mammal species. Whale flukes often can be used as identifying markings, as is the case for humpback whales. This is the method by which the famous Humphrey the whale was identified in three separate sightings.

The koala is broadly similar in appearance to the wombat (its closest living relative), but has a thicker coat, much larger ears, and longer limbs. The koala has large, sharp claws to assist with climbing tree trunks. Weight varies from about 14 kg (31 lb) for a large southern male, to about 5 kg (11 lb) for a small northern female. The koala’s five fingers are arranged with opposable thumbs, providing better gripping ability. The first two fingers are positioned in apposition on the front paws, and the first three fingers for the hind paws. The koala is one of the few mammals (other than primates) that has fingerprints. Koala fingerprints are similar to human fingerprints; even with an electron microscope, it can be quite difficult to distinguish between the two.

The Crucifix Toad is a ground dwelling frog, which inhabits the arid areas of western New South Wales and Queensland. To survive long periods without water, the Crucifix Toad will bury itself underground and encase itself in a cocoon. Upon rain, they will emerge from the ground, and begin breeding in temporary ponds. The males call from within the pond to attract the female. The call is a “woop”. The development of the tadpole is rapid. This is to reduce the risk of them dying from the pond drying up.

The frog exudes a tacky and elastic “frog glue” onto its dorsal skin when provoked. Its purpose is uncertain; it may be intended to confuse and deter predators such as snakes, or to trap biting insects (which would later be consumed when the frog sheds and eats its skin). Male Crucifix Toads have been documented to use this glue to attach themselves onto the larger females during mating.

In North America, the moose range includes almost all of Canada, most of central and western Alaska, much of New England and upstate New York, the upper Rocky Mountains, Northeastern Minnesota, and Michigan’s Upper Peninsula and Isle Royale in Lake Superior. Isolated moose populations have been verified as far south as the mountains of Utah and Colorado. In 1978 a few breeding pairs were introduced in western Colorado, and the state’s moose population is now more than 1,000.

In Europe, moose are found in large numbers throughout Norway, Sweden, Finland and the Baltic States. They are also widespread through Russia. Small populations remain in Poland (Biebrza Nat. Park), Belarus and the Czech Republic.

A tattoo is a marking made by inserting ink into the layers of skin to change the pigment for decorative or other reasons. Tattoos on humans are a type of decorative body modification, while tattoos on animals are most commonly used for identification or branding. Tattooing has been practiced worldwide.